Field
This disclosure relates generally to micro-electro-mechanical systems and more specifically to stiction detection and recovery in a micro-electro-mechanical system (MEMS) device.
Related Art
Micro-electro-mechanical systems (MEMS) is a technology for making very small mechanical devices using integrated circuit processing technology. The small mechanical devices may include sensors for use in a variety of applications, such as pressure sensors and acceleration sensors. Stiction is an industry-wide problem in MEMS sensors, and can be a significant contributor to yield loss. Stiction is generally determined to result from the attraction of two surfaces for various reasons such as electrostatic attraction, Van der Wals, Capillary Hydrogen Bonding, friction, etc. Stiction results in the two surfaces sticking together, or bonding, so that a large force is required to separate them. Stiction can occur at manufacturing, or later in the field. Physical phenomenon causing stiction are numerous, but not well understood or controlled. Anti-stiction coatings are effective, but can wear out due to repetitive shocks, humidity, surface roughness, charging, etc. Sensitive, low-G sensors are especially vulnerable because the restoring force of the spring is low and cannot overcome a strong adhesion force. At the final test stage of production, it is highly desirable to be able to screen products, but this may not be possible in some package designs where the MEMS element is not directly accessible with test equipment. In the field, it is desirable in some high reliability applications to provide the capability to detect stiction and even recover from it.